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    Subject[PATCH v3 22/25] misc: fastrpc: fix common struct sg_table related issues
    Date
    The Documentation/DMA-API-HOWTO.txt states that dma_map_sg returns the
    numer of the created entries in the DMA address space. However the
    subsequent calls to dma_sync_sg_for_{device,cpu} and dma_unmap_sg must be
    called with the original number of the entries passed to dma_map_sg. The
    sg_table->nents in turn holds the result of the dma_map_sg call as stated
    in include/linux/scatterlist.h. A common mistake was to ignore a result
    of the dma_map_sg function and don't use the sg_table->orig_nents at all.

    To avoid such issues, lets use common dma-mapping wrappers operating
    directly on the struct sg_table objects and adjust references to the
    nents and orig_nents respectively.

    Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
    ---
    For more information, see '[PATCH v3 00/25] DRM: fix struct sg_table nents
    vs. orig_nents misuse' thread: https://lkml.org/lkml/2020/5/5/187
    ---
    drivers/misc/fastrpc.c | 4 ++--
    1 file changed, 2 insertions(+), 2 deletions(-)

    diff --git a/drivers/misc/fastrpc.c b/drivers/misc/fastrpc.c
    index e3e085e..0a3e02aa 100644
    --- a/drivers/misc/fastrpc.c
    +++ b/drivers/misc/fastrpc.c
    @@ -518,7 +518,7 @@ static struct fastrpc_invoke_ctx *fastrpc_context_alloc(

    table = &a->sgt;

    - if (!dma_map_sg(attachment->dev, table->sgl, table->nents, dir))
    + if (!dma_map_sgtable(attachment->dev, table, dir))
    return ERR_PTR(-ENOMEM);

    return table;
    @@ -528,7 +528,7 @@ static void fastrpc_unmap_dma_buf(struct dma_buf_attachment *attach,
    struct sg_table *table,
    enum dma_data_direction dir)
    {
    - dma_unmap_sg(attach->dev, table->sgl, table->nents, dir);
    + dma_unmap_sgtable(attach->dev, table, dir);
    }

    static void fastrpc_release(struct dma_buf *dmabuf)
    --
    1.9.1
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